1. Field of the Invention
The present invention relates to a plasma processing system and a plasma processing method.
2. Related Background Art
In semiconductor fabrication processes, plasma processing systems which make required processing on semiconductor wafers (herein after simply called a wafer), objects-to-be-processed with plasmas are used.
Such plasma processing systems include those using inductive coupled plasmas (ICP) and those using capacitive coupled plasmas (CCP). The inductive coupled plasmas, which have higher plasma density than the capacitive coupled plasmas and have 10-20 V bias voltages which are lower than 100-200 V bias voltages of the capacitive coupled plasmas, can make highly efficient processing on wafers with little damage.
FIG. 5A is a sectional view of one example of the conventional plasma etching systems using the inductive coupled plasmas. The plasma etching system 200 comprises a chamber 201 having a susceptor 203 disposed inside for a wafer to be mounted on, a belljar 202 disposed on the chamber 201 with the interior communicated with the interior of the chamber 201, an antenna 205 wound on the outer periphery of the belljar 202, a high-frequency bias electric power source 204 connected to the susceptor 203, and a high-frequency electric power source 206 connected to the antenna 205. High-frequency electric power is supplied to the antenna 205 from the high-frequency electric power source 206, whereby induced electromagnetic fields are generated in the belljar 203 to generate plasmas of a processing gas. The wafer is processed with the plasmas.
However, in such plasma etching system 200, electric fields which are slant from the antenna 205 toward the susceptor 203 as indicated by the arrow in FIG. 5A, and the slant electric fields cause the etchant to be incident on the wafer surface as shown in FIG. 5B especially immediately after the plasmas are ignited. Resultantly, problems that configurations of micronized patterns are broken, and that electrons are slantly incident on the wafer surface, and charges are accumulated.
As means for removing the slant electric fields which is a cause for such problems, Specification of Japanese Patent Application Unexamined Publication No. 1993-206072, for example, discloses the use of a Faraday shield. As exemplified in FIG. 5C, the Faraday shield 207 is a cylindrical member of a conductor disposed between the belljar 202 and the antenna 205 of the plasma etching system 200′ and acts to short the components parallel with the axial direction of the Faraday shield 207 to remove the vertical components of the electric fields, whereby the generation of the slant electric fields is prevented. However, thus removing the vertical electric fields weakens the electric components effective to ignite the plasmas, which causes a problem of making the plasma ignition difficult.
In view of such circumferences, the present invention provides a plasma processing system and a plasma processing method which use inductive coupled plasmas and are free from the problems due to the slant electric fields generated immediately after plasmas have been ignited. An other object of the present invention is to provide a plasma processing system and a plasma processing method which can ignite the plasmas without failure even with the use of a Faraday shield in the conductive coupled plasma system.